IKONOS imagery was purchased to support the Pacific Islands Geographic Information System (GIS) project and the National Ocean Service's (NOS) coral mapping activities. One-meter panchromatic and four-meter multi-spectral data were purchased for each study area. A digital vector shoreline was manually digitized from the one-meter panchromatic imagery to provide accurate, up-to-date shoreline data.

The vectorized shoreline data was derived from the one-meter panchromatic IKONOS imagery. Those areas of the coastline that were obscured by cloud cover were derived from United States Geological Survey (USGS) Digital Raster Graphics (DRGs)

Planar coordinates are encoded using Coordinate Pair
Abscissae (x-coordinates) are specified to the nearest 0.000064
Ordinates (y-coordinates) are specified to the nearest 0.000064
Planar coordinates are specified in meters

The horizontal datum used is D_North_American_1983_HARN.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.

The Pacific Islands Geographic Information System (GIS) project is a multiyear initiative designed to increase the use of GIS and related spatial technology in the coastal resource management programs of the Territories of American Samoa and Guam, the Commonwealth of the Northern Mariana Islands (CNMI), and the State of Hawaii. The project will focus on personnel, training, equipment, software, data, and applications. Where appropriate, other related activities in the region will be incorporated into the effort.

During the vectorization process, the satellite imagery was displayed on a computer screen using ESRI's ArcGIS 8.2 software. In order to obtain the highest degree of accuracy from the imagery, the one-meter panchromatic imagery was used as a base layer for digitizing. In an effort to better visualize the land-water interface, the one-meter imagery was overlaid on top of the four-meter multispectral imagery using a 35 % transparency value. The near-infrared band (Band 4) was used in the display of the multispectral imagery. The resultant base layer contained the one-meter resolution of the panchromatic imagery and the colorization of the four-meter imagery. The display was zoomed to the image resolution of the panchromatic imagery and the shoreline was manually digitized. All lines are coded with length, ID, origin, and source

Note - Areas of the shoreline that were obscured by cloud cover were digitized from USGS Digital Raster Graphics (DRGs). The USGS DRG for Manua had to be adjusted in the x and y directions using ERDAS Imagine 8.5 to match the IKONOS imagery.

The completed shoreline dataset was sent to the on-island technical assistant in American Samoa for review and adjustment. Using the same IKONOS imagery and DRG datasets, as well as GPS data and personal knowledge of the subject area, the technical assistant was able to make adjustments to the shoreline. These adjustments were needed in areas where the land-water interface was unable to be determined clearly due to cloud cover or shadow.

The data were created by delineating the shoreline off of IKONOS panchromatic digital satellite imagery collected in 2001. The horizontal resolution of the digital imagery is 1 meter. The original scale of the imagery was 1:3780. During orthorectification of the IKONOS imagery, 60 ground control points were used to determine the circular error (CE) at a 90% confidence level. For Pacific Islands, Tutuila, American Samoa, IKONOS data, 2001 the circular error is 2.7 meters for the Panchromatic data set.

This shoreline dataset of Tutuila is dependent on the shoreline as delineated on 2001 IKONOS digital satellite imagery from Space Imaging, LLC. The position of the shoreline might change as the natural land changes or better maps and more current aerial photography become available.

These data are believed to be logically consistent, though no tests were performed. All arcs were snapped by the nodes to create consistently tied strings without node dangles. Line geometry is topologically clean.

Data set is not for use in litigation. While efforts have been made to ensure that these data are accurate and reliable within the state of the art, NOAA, cannot assume liability for any damages, or misrepresentations, caused by any inaccuracies in the data, or as a result of the data to be used on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

Users must assume responsibility to determine the appropriate use for these data.
NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA can not assume liability for and damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.